Process for preparing high strength fabricated articles from aluminumbase alloys containing magnesium and copper



United States Patent Ufitice 3,291,654 Patented Dec. 13, 1966 PRUtIESS FQR PREPARHNG HIGH STRENGTH FABRICATED ARTHQLES FROM ALUMINUM- BASE ALLQYS CONTAINING MAGNESEUM AND COPPER George S. Foerster, Midland, Mich, assignor to The Dow Chemical Company, Midland, Mich, a corporation of Delaware No Drawing. Fiied Dec. 26, 1963, Ser. No. 333,655

12 Claims. (Cl. 14812.7)

This invention relates to aluminum-base alloys and more particularly concerns a novel process for making high strength fabricated articles from aluminumbase ternary alloys containing magnesium and copper.

The object of the present invention, then, is to provide a process for preparing high strength fabricated articles from such alloys and particularly for making extru-ded articles from aluminum-base pelleted alloys containing magnesium and copper.

It has been found in accordance with the present invention that the above and other objects and advantages can be obtained by subjecting an aluminum-base ternary alloy containing magnesium in an amount within the range of from about 0.5 to about 3 percent, and copper in an amount Within the range of from about 6.2 to about 20, preferably 7.5 to 12 percent, to the action of a process comprising the steps of rapidly solidifying the molten alloy, hot working the alloy so-solidified into a useful shape, solution heat treating the worked article, followed by rapid quenching and aging. Articles so-made exhibit unusually high strength and other desirable properties.

The aluminum base ternary alloys used in the present invention are ordinarily prepared using conventional alloying and melting techniques as are commonly practiced in the aluminum art. The amount of magnesium to be employed in the alloy, being as aforesaid within the range of from 0.5 to 3 percent, is in general preferably used in increasing amounts as the copper content is increased. That is, as more copper is used, correspondingly an increase in magnesium is employed, depending on the particular alloy desired, the exact proportions of magnesium and copper to be used being readily determined by one skilled in the art.

Rapid solidification of the alloy may preferably be accomplished, for example, by jet or disc-type atomizing of the molten alloy either in air or in an atmosphere inert with respect to the alloy, such as, for example, argon. When atomized, though not critical, the pellets should preferably be of a size such that at least about 50 percent are capable of passing through a number 20 screen, and even more preferably a number 100 mesh screen (U.S. Standard Sieve Series). Pellets of a size greater than these, i.e., more coarse pellets are, of course, suitable for use in the present invention. However, the articles produced therefrom usually exhibit somewhat lower strength values than those prepared from finer pellets.

Though atomizing is preferred as a means of rapidly solidifying the alloys used in the present invention, other means may also be employed such as, for example, casting the alloy into thin-walled cold molds or injection molding.

After rapid solidification the alloy may be hot worked int-o a useful shape as, for example, by forging, hot rolling,

or preferably by extruding, particularly when the alloy has been pelleted. When employing the latter and preferred method of hot working, a batch of the pellets is normally first preheated to a temperature within the range of from about 700to about 900 F., charged into the container of an extrusion press, and extruded through an aperture having the desired cross section, the container being at a temperature of from about 600 to 850 F. and preferably 750 to 850 F. If desired, however, the pellets either hot or cold, may be precompacted in a separate step as by squeezing in the container of said press prior to displacement. In any event, compaction occurs as a consequence of performing the displacement operation. Though preheating of the pellets as aforesaid is preferred, the cold pellets may be charged into the hot container and then extruded.

Following hot working, the alloy is then solution heat treated at a temperature within the range of from about 900 F. to about 960 F. and preferably at about 915 F. to 930 F. for a period of time, when the copper content does not exceed about 7.5 percent, within the range of from about 1 minute to about 45 minutes, and for a time within the range of from about 1 minute to 2 hours when the copper content exceeds about 7.5 percent. The hot article is thereafter rapidly quenched as, for example, with water as a coolant.

Following solution heat treating and rapid quenching, the aluminum-base ternary articles of the present invention are conventionally aged by exposure to room temperature (about 25 C.) for at least about one day and preferably at least about 2 days, or, by heating to a temperature of from about 300 to about 350 F. for a period within the range of from about 4 to about 24 hours, preferably 10 to 20 hours.

Other metals conventionally alloyed with aluminum may also be added to the present alloys, such as, for example, manganese, in an effective amount up to about 2.0 percent by weight or chromium in an effective amount up to about 1.0 percent.

The following examples serve to further illustrate the novel process of the present invention but are not to be construed as limiting it thereto.

Various aluminurn base alloys consisting essentially of copper and magnesium, in the amounts as indicated in Table I below, the balance being aluminum, were prepared by conventional techniques and jet atomized into pellets (P) approximately percent of which were capable of passing a number 20 mesh screen. A batch of pellets of each alloy prepared was preheated 1 to 2 hours at 800 F. then charged into the container of an extrusion press, the container having the same temperature, and extruded at a speed of 5 feet per minute into strips having a rectangular cross section of 0.2 inch by 1 inch. Subsequently, the resulting extruded strips were solution heat treated (SHT) at the temperature and times indicated, rapidly quenched, then aged for 16 hours at the temperature indicated in Table I.

Standard test pieces of the processed strips for each alloy were prepared and then tested at room temperature, whereupon, the percent elongation (percent E) (using a 2-inch gauge length), tensile yield strength (at a 0.2 percent deviation from the modulus) and tensile strength were determined.

3 For comparison purposes ingot-s of some of the alloys were also prepared and processed similarly to the pelleted alloys.

the balance being aluminum, which comprises the steps of atomizing the alloy into pellets from the molten state, extruding the so-pelleted alloy, thereby to hot Work the TABLE I Al-base alloy Solution Heat Treating Aging Tension Tests Example Percent E Percent Percent Form Temp, Time Temp, Tune TYS TS Mg Cu F. (hours) F. (hours) 1. 5 5.0 920 0. 5 320 16 26 38 59 1. 5 7.0 P 920 0. 5 340 16 15 47 70 1. 5 7. P 920 1. 0 320 16 18 34 68 1. 7.0 I 920 0. 5 340 16 2O 40 61. 1. 5 7. 0 I 920 1. 0 320 16 22 36 5S 1. 5 8. 5 P 920 O. 5 340 16 47 70 1. 5 8. 5 P 920 1. 0 320 16 16 45 70 1. 5 8. 5 I 920 0. 5 340 16 18 39 59 1. 5 8. 5 I 920 1. 0 320 16 21 37 60 1. 5 15.0 I? 920 1. 0 320 16 8 48 70 1. 5 15. 0 I 920 1. 0 320 16 8 42 58 The figures in Table I, particularly Examples 1, 2, 5, 6 and 9, clearly illustrate the high strength values obtained in the alloys of the present invention. The ingot examples illustrate the comparatively lower strengths obtained in similar alloys not processed in accordance with the present invention. In addition, Example 1, when compared to Example 2, illustrates the preferability of solution heat treating the alloys for shorter times when the copper content is below about 7.5 percent.

Various modifications and changes can be made in the present invention without departure from the spirit or scope thereof and it is understood that I limit myself only as defined in the appended claims.

I claim:

1. A method of preparing a high strength aluminumbase fabricated alloy article consisting by weight essentially of magnesium in an amount within the range of from about 0.5 to about 3 percent and copper in an amount within the range of from about 6.2 to about percent, the balance being aluminum, which comprises the steps of rapidly solidifying the alloy from the molten state, hot Working the alloy into a useful shape, solution heat treating the so-worked alloy, followed by rapid quenching and aging, thereby to prepare a fabricated high strength aluminu m-base alloy article.

2. The method of claim 1 wherein the copper in the alloy is present in an amount within the range of from about 7.5 to about 12 percent; and magnesium in an amount within the range of from about 1.0 to about 2.0 percent.

3. The method of claim 1 wherein the molten alloy is rapidly solidified by atomizing into pellets.

4. The method of claim 1 wherein the hot working is accomplished by extruding the alloy.

5. The method of claim 1 wherein the solution heat treating is carried out at a temperature within the range of from about 900 to about 960 F. for a period of time within the range of from about 1 minute to two hours.

6. The method of claim 1 wherein the aging is carried out at a temperature Within the range of from about 300 to about 350 F. for a period of time within the range of from about 4 to about 24 hours.

7. A method of preparing .a high strength aluminurn base alloy extruded article consisting by weight essentially of an amount of magnesium within the range of from about 0.5 to about 3 percent, and an amount of copper within the range of from about 6.2 to about 20 percent,

alloy into a useful shape, solution heat treating the extruded alloy, and rapidly quenching and aging the alloy to prepare a high strength aluminum-base extruded article.

8. The method of claim 7 wherein the copper in the alloy is present in an amount within the range of from about 7.5 to about 12 percent.

9. The method of claim 7 wherein the pelleted alloy is extruded at a temperature within the range of from about 600 to about 850 F. v

10. The method of claim 7 wherein the extruded alloy is solution heat treated at a temperature within the range of from about 900 to about 960 F. for a period of time within the range of from about 1 minute to about 2 hours.

11. The method of claim 7 wherein the solution heat treated article after quenching is aged at a temperature within the range of from about 300 F. to about 350 F. for a period of time within the range of from about 4 to about 24 hours.

12. A method of preparing a high strength aluminumbase alloy extruded article consisting by weight essentially of an amount of magnesium within the range of from about 1.0 to about 2.0 percent and an amount of copper within the range of from about 7.5 to about 12, the balance being aluminum, which comprises the steps of atomizing the alloy into pellets from the molten state, extruding the pelleted alloy at a temperature within the range of from about 750 to about 850 F.. solution heat treating the alloy at a temperature within the range of from about 915 to about 930 F. for a period of time within the range of from about 1 minute to about 2 hours, and aging the so-treated alloy at a temperature within the range of from about 320 to about 340 F. for a period within the range of from about 10 to about 20 hours.

References Cited by the Examiner UNITED STATES PATENTS 3,177,073 4/1965 Foerster 148-32.5 X

FOREIGN PATENTS 599,607 6/1960 Canada.

DAVID L. RECK, Primary Examiner.

H. F. SAITO, Assistant Examiner. 

12. A METHOD OF PREPARING A HIGH STRENGTH ALUMINUMBASE ALLOY EXTRUDED ARTICLE CONSISTING BY WEIGHT ESSENTIALLY OF AN AMOUNT OF MAGNESIUM WITHIN THE RANGE OF FROM ABOUT 1.0 TO ABOUT 2.0 PERCENT AND AN AMOUNT OF COPPER WITHIN THE RANGE OF FROM ABOUT 7.5 TO ABOUT 12, THE BALANCE BEING ALUMINUM, WHICH COMPRISES THE STEPS OF ATOMIZING THE ALLOY INTO PELLETS FROM THE MOLTEN STATE, EXTRUDING THE PELLETED ALLOY AT A TEMPERATURE WITHIN THE RANGE OF FROM ABOUT 750* TO ABOUT 850* F., SOLUTION HEAT TREATING THE ALLOY AT A TEMPERATUE WITHIN THE RANGE OF FROM ABOUT 915 TO ABOUT 930* F. FOR A PERIOD OF TIME WITHIN THE RANGE OF FROM ABOUT 1 MINUTE TO ABOUT 2 HOURS, AND AGING THE SO-TREATED ALLOY AT A TEMPERATURE WITHIN THE RANGE OF FROM ABOUT 320 TO ABOUT 340* F. FOR A PERIOD WITHIN THE RANGE OF FROM ABOUT 10 TO ABOUT 20 HOURS. 